Worldwide PC shipments are down, tablets continue to change the PC landscape, and the Mac has increased sales in the U.S. Those are the key findings in Gartner's report on the fourth quarter, released Monday.

Gartner's report agrees with a similar one from IDC on Thursday, in that both showed a global drop in PC sales -- 4.9 percent for Gartner, 6.4 percent for IDC. And both show the continuing importance of tablets.

But Gartner found that Apple sold 5.4 percent more Macs in the U.S. in the fourth quarter of 2012 compared with 2011, boosting market share to 12.3 percent, while IDC found a 0.2 percent drop that kept Mac's market share at 11.4 percent. Next week, Apple is expected to reveal its actual sales figures for the quarter.

Exception, Not the Norm

Overall computer sales in the U.S. declined by 2.1 percent, according to Gartner, compared with Q4 2011.

Mikako Kitagawa, principal analyst at Gartner, said in a statement that, while tablets have "dramatically changed" the overall picture for PCs, it is "not so much by 'cannibalizing' PC sales," as it is because PC users are turning to tablets instead of replacing older PCs.

"Whereas once we imagined a world in which individual users would have both a PC and a tablet as personal devices," she added, "we increasingly suspect that most individuals will shift consumption activity to a personal tablet, and perform creative and administrative tasks on a shared PC." Kitagawa predicted that some individuals will have both a PC and a tablet, but they "will be the exception and not the norm."

If accurate, this analysis means that many users will simply let their PC "age out," as Gartner said, and then buy a tablet when they are ready for a new computing device. In this scenario, the installed base for PCs will continue to decline, as the availability of low-cost tablets continues to grow.

Promising Platform

Gartner also noted that Windows 8 "did not have a significant impact on PC shipments in the fourth quarter." Sales of both mobile and desktop PCs declined in the fourth quarter, by 11 percent and 6 percent respectively year over year, but Gartner said that all-in-one form factors from Asus, Lenovo and Hewlett-Packard "look like a promising platform for the future."

By ranking in units shipped worldwide, HP is once again first, having temporarily lost it last quarter to now-second place holder Lenovo. HP and Lenovo do not have much spread between them -- 16.2 percent and 15.5 percent, respectively. Dell is third with 10.2 percent, followed by Acer Group (9.5 percent), Asus (7.2 percent) and "others" at 41.4 percent. Gartner counts mini-notebooks but not media tablets like the iPad in its figures.

Laura DiDio, an analyst with Information Technology Intelligence Consulting, said the reports from Gartner and IDC support the overall perception that buyers are not flocking to Windows 8, but she added that this was "not unusual" for the business market, since it "usually is slow going" for companies to upgrade, especially if new form factors, interaction, applications or drivers are involved.

DiDio added that, since tablets are not "optimized for productivity" in most cases, she can accept Gartner's reasoning about consumption for tablets and more productive tasks on a PC, but not the idea that many PC users will become tablet-only. Instead, she suggested, it might well be a situation where existing PCs are fine for many users, who are adding a tablet when they want to upgrade their computing capacity.